Science (English Medium) Class 11 - CBSE Question Bank Solutions

A steel wire of cross-sectional area 0.5 mm² is held between two fixed supports. If the wire is just taut at 20°C, determine the tension when the temperature falls to 0°C. Coefficient of linear expansion of steel is 1.2 × 10^–5 °C^–1 and its Young's modulus is 2.0 × 10^–11 Nm^–2.

A steel ball that is initially at a pressure of 1.0 × 10⁵ Pa is heated from 20°C to 120°C, keeping its volume constant.
Find the pressure inside the ball. Coefficient of linear expansion of steel = 12 × 10^–6 °C^–1and bulk modulus of steel = 1.6 × 10¹¹ Nm^–2.

Which of the following example represent periodic motion?

A swimmer completing one (return) trip from one bank of a river to the other and back.

Which of the following example represent periodic motion?

A freely suspended bar magnet displaced from its N-S direction and released.

Which of the following example represent periodic motion?

A hydrogen molecule rotating about its center of mass.

Which of the following example represent (nearly) simple harmonic motion and which represent periodic but not simple harmonic motion?

The rotation of the earth about its axis.

Which of the following example represent (nearly) simple harmonic motion and which represent periodic but not simple harmonic motion?

A motion of an oscillating mercury column in a U-tube.

Which of the following example represent (nearly) simple harmonic motion and which represent periodic but not simple harmonic motion?

The motion of a ball bearing inside a smooth curved bowl, when released from a point slightly above the lowermost point.

Given below are some functions of x and t to represent the displacement (transverse or longitudinal) of an elastic wave. State which of these represent (i) a traveling wave, (ii) a stationary wave or (iii) none at all:

y = 2 cos (3x) sin (10t)

Given below are some functions of x and t to represent the displacement (transverse or longitudinal) of an elastic wave. State which of these represent (i) a traveling wave, (ii) a stationary wave or (iii) none at all:

`"y" = 2sqrt(x - "vt")`

Given below are some functions of x and t to represent the displacement (transverse or longitudinal) of an elastic wave. State which of these represent (i) a traveling wave, (ii) a stationary wave or (iii) none at all:

y = 3 sin (5x – 0.5t) + 4 cos (5x – 0.5t)

The radius of atom is of the order of 1 Å and the radius of nucleus is of the order of fermi. How many magnitudes higher is the volume of atom as compared to the volume of nucleus?

1. The earth-moon distance is about 60 earth radius. What will be the diameter of the earth (approximately in degrees) as seen from the moon?
2. Moon is seen to be of (½)°diameter from the earth. What must be the relative size compared to the earth?
3. From parallax measurement, the sun is found to be at a distance of about 400 times the earth-moon distance. Estimate the ratio of sun-earth diameters.

The distance of a galaxy is of the order of 10²⁵ m. Calculate the order of magnitude of time taken by light to reach us from the galaxy.

In an experiment to estimate the size of a molecule of oleic acid 1 mL of oleic acid is dissolved in 19 mL of alcohol. Then 1 mL of this solution is diluted to 20 mL by adding alcohol. Now 1 drop of this diluted solution is placed on water in a shallow trough. The solution spreads over the surface of water forming one molecule thick layer. Now, lycopodium powder is sprinkled evenly over the film and its diameter is measured. Knowing the volume of the drop and area of the film we can calculate the thickness of the film which will give us the size of oleic acid molecule.

Read the passage carefully and answer the following questions:

1. Why do we dissolve oleic acid in alcohol?
2. What is the role of lycopodium powder?
3. What would be the volume of oleic acid in each mL of solution prepared?
4. How will you calculate the volume of n drops of this solution of oleic acid?
5. What will be the volume of oleic acid in one drop of this solution?

How many astronomical units (A.U.) make 1 parsec?

Consider a sunlike star at a distance of 2 parsecs. When it is seen through a telescope with 100 magnification, what should be the angular size of the star? Sun appears to be (1/2)° from the earth. Due to atmospheric fluctuations, eye can’t resolve objects smaller than 1 arc minute.

Mars has approximately half of the earth’s diameter. When it is closest to the earth it is at about 1/2 A.U. from the earth. Calculate what size it will appear when seen through the same telescope.

Refer to the graphs in figure. Match the following.

Graph	Characteristic
(a)	(i) has v > 0 and a < 0 throughout.
(b)	(ii) has x > 0 throughout and has a point with v = 0 and a point with a = 0.
(c)	(iii) has a point with zero displacement for t > 0.
(d)	(iv) has v < 0 and a > 0.

A ball is dropped and its displacement vs time graph is as shown figure (displacement x is from ground and all quantities are +ve upwards).

1. Plot qualitatively velocity vs time graph.
2. Plot qualitatively acceleration vs time graph.